An understanding of morphological and genetic diversity of sweet potato landraces is fundamental to any breeding program in a country. Fifty-nine sweet potato accessions from three eco-geographical populations of northern, south eastern and southern Malawi were examined using ten Simple Sequence Repeats (SSR) loci and seven International Board for Plant Genetic Resources (IBPGR) descriptors of sweet potato. The study generated a total of 30 alleles with a mean of 3 alleles per locus and a range of 2 to 5 alleles per locus. The primers were highly polymorphic and discriminatory with Polymorphism Information Content (PIC) mean of 0.55 and a range of 0.29 to 0.75, implying that allelic diversity and molecular relationships revealed by the study are strongly supported. Mean Nei’ gene diversity (h=0.30) and Shannon information index (I=0.43) showed moderate genetic diversity of the populations with landraces (h=0.32; I=0.47) exhibiting more genetic diversity than introductions (h=0.25; I=0.38). SSR and morphological markers differently distinguished the accessions as evidenced by poor correspondence of genetic and morphological distance matrices (Mantel’ Test, r=0.1095). However, cluster analysis indicated high variability among accessions at morphological (50% dissimilarity) and genetic (64% dissimilarity) level. Therefore, Malawian sweet potato landraces harbour considerably high morphological and genetic diversity warranting use in breeding programs.
Key words: Simple sequence repeats (SSR) loci, morphological diversity, sweet potato accessions, genetic diversity, descriptors, polymorphism.
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